Vitamin A is known to possess skin conditioning properties. U.S. Pat. No. 4,603,146 refers to Vitamin A acid (retinoic acid) for retarding the effects of aging of the skin. For a general discussion of dermatological uses of Vitamin A, reference may be had to Thomas et al., J. Am. Acad. Derm., Vol. 4, No. 5 (1981).
Vitamin A is a mild irritant. It is generally applied to the skin in a suitable non-toxic, dermatologically acceptable carrier in an amount and at a frequency which are insufficient to cause excessive irritation of the skin. Most compositions for applying Vitamin A to the skin are in the form of cloudy emulsions or grease-like masses.
Cosmetic and pharmaceutical compositions for applying biologically active materials to the skin typically include a carrier for the active materials in the composition. The selection of a suitable carrier for use in compositions in which the release of biologically active materials is controlled is complicated by the fact that the carrier should not interfere with (and preferably enhances) the ability of the composition to release its active material at a suitable rate. In addition, it is desirable if the carrier (or some other component of the composition) functions to enhance the penetration of the composition's biologically active materials to the desired layers of the skin.
U.S. Pat. No. 4,301,023 (the '023 patent) refers to a mixture of two or more cholesteric liquid crystal compounds, suspended in an oleaginous carrier or in an aqueous emulsion, for moisturizing and softening the skin. The '023 patent does not refer to the use of such liquid crystals as a delivery vehicle for biologically active materials. Neither does the '023 patent disclose that the liquid crystals enhance the penetration of and stabilize active materials contained therein.